Resonant pulse jet burner



June 3, 1969 F, HAAG ETAL I 3,447,878

RESONANT PULSE JET BURNER Filed Nov. za, 1967 F RANZ HAAG LUDWIG HUBEP fhvir' ATTORNEy United States Patent O U.S. Cl. 431-1 Clairns ABSTRACT OF THE DISCLOSURE A resonant pulse jet burner having a cylindrical combustion chamber one end of which is closed and accommodates a spark plug and the other end of which is connected With a resonator. The conduit which supplies a mixture of oxygen and gaseous fuel (particularly natural gas of low combustiblity) has a spoon-shaped outlet portion extending into the combustion chamber closer to the spark plug than to the resonator and having an open side which faces the closed end of the combustion chamber. The configuration of the outlet portion and of the closed end of the combustion chamber is such that the mixture flows in a circular path and surrounds a hot core of gaseous products which circulate past the open side of the Outlet portion and insure immediate ignition of freshly admitted mixture as well as satisfactory combustion of such mixture. The products of combustion flow laterally past the outlet portion and into the resonator.

Background of the invention The present invention relates to improvements in resonant pulse jet burners, particularly to improvements in burners which utilize a mixture of oxygen and gaseous fuel.

It is already known to preheat a mixture of gaseous fuel and oxygen prior to admission into the combustion chamber of a resonant pulse jet burner. Such preheating is intended to insure ready ignition and satisfactory combustion and can take place by conveying the mixture through a funnel which extends into the combustion chamber. It is also known to provide the burner with means for creating turbulence in the mixture of fuel and oxygen and to thus enhance the combustion in the interior of the combustion chamber. Burners Which utilize liquid fuel are often provided with a venturi which admits fuel into the combustion chamber and Whose Outlet is located in the axis of the combustion chamber. One end wall of such combustion chamber is provided with devices which prevent backfiring and the other end of the combustion chamber is open and communicates With a resonator. The combustion chamber accommodates a spark plug or another suitable igniter. All of the just described burners are employed mainly for combustion of fuels which are readily combustible and Whose combustiblity is substantially constant to make sure that the combustion will take place at an unchanging rate when the burner is in operation.

However, such Conventional burners are unsatisfactory when the combustiblity of fuel varies within a wide range, i.e., when a burner must burn readily combustible fuels as Well as fuels Which are more difiicult to ignite and whose complete combustion is diflicult to achieve. The problem is particularly acute When a burner is to be used for combustion of different types of gaseous fuels which are mixed With air. Such burners are often used as heat exchangers to heat Water for use in baths, kitchens and laundry rooms as well as for heating of water in central heating systems for private homes or other types of buildings. When the gas used in such burners is city gas, its combustion presents no series problems because such gas contains a relatively high percentage of hydrogen. However, when the same burner is to employ liquefied gas which is stored in bottles and/or natural gas which is less readily combustible than city gas, the combustion and/or ignition of the oxygen-gas mixture is far from satisfactory.

Summary of the invention It is an object of our invention to provide a resonant pulse jet burner Which can insure rapid ignition and satisfactory combustion of gases Which are much less readily combustible than normal city gas.

Another object of the invention is to provide a burner of the just outlined character Which is of simple, compact and inexpensive design and wherein satisfactory combustion of fuel is insured by the simple expedient of selecting an appropriate configuration and mounting for the conduit which Supplies a mixture of gaseous fuel and oxygen into the combustion chamber.

A further object of the present invention is to provide a burner which can be used for heating of water or for other purposes and which can be obtained by a simple and inexpensive modification of presently known burners.

An additional object of our invention is to provide a burner Which, though particularly suited for use With fuels whose combustiblity is not very satisfactory, can be used with equal advantage for combustion of city gas or like fuels Whose combustiblity is satisfactory.

In its simplest form, the improved burner comprises a preferably cylindrical combustion chamber one end of which is closed and accommodates a spark plug or another suitable igniter and the other end of which is connected with a resonator. The conduit which Supplies a mixture of fuel and oxygen comprises a substantially ladleor spoonshaped outlet portion which extends into the combustion chamber, preferably closer to the igniter than to the resonator, and has an open side facing the closed end of the combustion chamber to cause the outflowing mixture to flow in a substantially circular path which surrounds a turbulent core of hot fuel and combustion products serving to insure immediate ignition and complete combustion of the freshly admitted mixture.

The novel features Which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved burner itself, however, both as to its construction and its mode of Operation, together with additional features and advantages thereof, Will be best understood upon perusal of the following detailed description of a specific embodiment With reference to the accompanying drawing.

Brief description of the drawng FIG. l is a somewhat schematic side elevational view of an apparatus comprising two burners each of which embodies the present invention;

FIG. 2 is an enlarged fragmentary axial sectional view of one of the burners; and

FIG. 3 is a fragmentary horizontal view as seen in the direction of arrows from the line III-III of FIG. 2.

Description of the preferred embodiment Referring first to FIG. l, there is shown a resonant pulse jet combustion apparatus which comprises two burners and can be utilized as a heat exchanger for use in heating of circulating water, for example, to heat water for use in baths, kitchens and laundry rooms and/or for heating of Water in hot-water heating systems for homes or the like. The combustion apparatus of FIG. 1 comprises two burners each of which includes a combustion chamber (resp. 11) each of which is connected with a conduit (25, 26) which supplies a mixture of oxygen and gaseous fuel, the mixtures being drawn into the respective chambers when the system is in Operation. The lower ends of the combuston Chambers are connected with exhaust conduits 12, 13 which constitute two resonators and whose discharge ends are connected to a common Outlet 14. For the sake of simplicity, the customary soundabsorbent chambers which surround the combuston Chambers 10, 11 are not shown in FIG. 1. The medium (for example, water) which is to exchange heat .with the combuston products developing on combuston of the fuel-oxygen mixture is conveyed through a pipe 15 having an inlet 151 and an Outlet 152. The pipe 15 is coiled first around the combuston chamber 10 in a direction upwardly and away from the resonator 12, thereupon around the combuston chamber 11 in a direction toward the resonator 13, and finally around packages of laminations or fins 16, 17 provided externally on the resonators adjacent to their connections with the respective combustion Chambers.

When the combuston apparatus is in use, air is drawn from a feed chamber 20 through aid intakes 18, 19 which respectively form part of the aforementioned conduits 25, 26. Fuel is supplied by a supply conduit 21 which discharges fuel into a mixing chamber 22. This mixing chamber has two Outlets which respectively admit fuel to conduits 23, 24 communicating with the conduits 25, 26 upstream of the respective combuston chambers 10, 11. The fuel is mixed with air prior to entry into the respective combuston chamber.

FIGS. 2 and 3 illustrate the manner in which the supply conduit 26 discharges a mixture of gaseous fuel and oxygen (norrnally air) into the interior of the combuston chamber 11. The manner in which the supply conduit discharges a mixture of fuel and air into the combuston chamber 10 is the same as shown in FIGS. 2 and 3. The combuston chamber 11 resembles au elongated cylinder of circular cross section and comprises a cylindrical wall 112 the upper end of which is closed by an end wall 114 having a concave internal surface and accommodating a centrally located igniter here shown as a spark plug 32. The numeral 111 denotes in FIG. 2 the upper portion of the combuston chamber 11, i.e., that portion which is adjacent to its closed upper end. The lower end of the combuston chamber 11 is connected with the finned portion of the resonator 13 as shown in FIG. 1.

The lowermost part 28 of the conduit 26 comprises an inlet portion 281 which is located externally of the combustion chamber 11, a tubular portion 282 which extends substantially radially through the cylindrical wall 112, and a substantially spoonor ladle-shaped Outlet portion 30 which is located in the upper portion 111 of the combustion chamber 11, i.e., near to the closed upper end than to the resonator 13. The inlet portion 281 is introduced into a short sleeve 113 which is accommodated in a hole of the cylindrical wall 112 and is detachably coupled to the inlet portion 281 by a Strap 29. The tubular portion 282 is integral with the Outlet portion 30 and is telescoped into the discharge end of the inlet portion 281. By loosening the strap 29, an operator can withdraw the Outlet portion 281 and the portions 282, 30 from the sleeve 113 which latter can be welded or otherwise sealingly secured to the wall 112. The length of that part of the conduit 26 which extends into the combuston chamber 11 can approximate or can even exceed threefourths of the diameter of the wall 112.

The open side 31 of the ladle-shaped Outlet portion 30 faces the end wall 114 and spark plug 32. The area of the open side 31 at most equals half the cross-sectional area of that portion of the cylinder 112 Which accommodates the outlet portion 30. The open side 31 is formed by removing a portion of an Originally tubular part of the Outlet portion 30 and the edges bounding the open side 31 are preferably located in a plane which is normal to the axis of the wall 12, i.e., which is substantially parallel to the axis of the tubular portion 282. The length of this open side 31 preferably at least equals the radius of the wall 112. FIG. 3 shows that the width of the open side 31 need not exceed the diameter of the Outlet portion 30 but the latter is provided with an upwardly extending billor beak-shaped extension or projection 301 which is remote from the tubular portion 282. The edges of the extension 301 are located slightly above the edges bounding the major part of the open side 31.

The tubular portion 2-82 has a flat 302 which is immediately adjacent to the open side 31 and tapers in a direction away from the extension 301. In accordance with a presently preferred embodiment of our invention, the distance between the open side 31 and the end wall 114 approximates the diameter of the cylindrical wall 112.

The Operation is as follows:

The lowermost part 28 of the supply conduit 26 admits a mixture of oxygen and gaseous fuel, and such mixture leaves the conduit 26 at the open side 31 of the Outlet portion 30. The right-hand surface of the extension 301 (as viewed in FIG. 2) deflects the mixture upwardly and causes it to flow in a substantially circular path. Such movement of the mixture in a circular path is assisted by the concave internal surface of the wall 114 at the closed upper end of the combuston chamber 11. The mixture is ignited by sparks produced between the electrodes of the igniter 32 which, however, is operative only for a short time at the start of the Operation because the ignition of mixture proceeds automatically when the burner is heated up. During normal Operation (when the igniter is inactive), ignition takes place along the entire circular path of the mixture in the combuston chamber 11. Combustion of freshly admitted mixture then begins immediately at the edges of the Outlet portion 30 and, after travelling without any shock along an arc of about 270 degrees, the products of combuston flow laterally past both sides of the Outlet portion 30 and into the lower part of the combustion chamber 11 to enter the resonator 13. The Outlet portion 30 divides such products into two identical or similar streams. The area within the circular path accommodates a hot core which contains circulating turbulent gases spaced from the walls of the combuston chamber 11 and flowing past the open side 31 of the Outlet portion to be replenished with freshly admitted oxygen and fuel. This core contains active (burnable) ingredients which assist the combuston of freshly admitted mixture leaving the Outlet portion 30. The core remains in the combuston chamber during the entire Operation of the burner and during exhausting, mainly due to inertia of its contents, and continues `to circulate immediately past the open side 31 of the Outlet portion 30. The important function of the core is to insure satisfactory ignition and satisfactory combuston of gases which are not as readily combustible as city gas.

The axis of the aforementioned circular path is normal to the axis of the cylindrical wall 112 and the Stream of gases which move past the internal surface of the end wall 114 flows back toward the open side of the Outlet portion 31. This is important because the stream of hot gases comes in contact with the freshly admitted mixture. Such mixture is also contacted by active ingredients of the hot core which is surrounded by and circulates in the same direction as the main Stream. The core is formed in the center of the upper portion 111 above the open side 31 of the Outlet portion 30: Since the core does not come into appreciable contact with the walls of the combuston chamber 11, turbulence created by the configuration of the Outlet portion 30 can develop without appreciable drop in pressure. Moreover, the walls of the combuston chamber 11 cannot withdraw heat from the circulating core so that the contents of the core can circulate at high speed toward and past the open side 31. This is in contrast to presently known burners wherein turbulence develops while the gases flow past the walls of the combuston chamber and thereby undergo considerable Cooling action.

Thercfore, the mixture issuing at the open side 31 can be ignited more readily than in Conventional burners even if the combustibility of gases in the mixture entering the chamber 11 is rather low.

The feature that the area of the open side 31 should not exceed half the cross-sectional area of the cylindrical wall 112 in the region Where the chamber 11 accommodates the outlet portion 30 is desirable to insure that the core develops in the center of the area between the end wall 114 and the outlet portion. The flat 302 enhances the flow of comhustion products into the lower part of the chamber 11 and ltoward 'the resonator 13. The main purpose of the extension 301 is to cooperate with the wall 114 in the formation of acircular gas flow.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteritsics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a resonant pulse jet burner, a combination comprising a comhustion chamber having a closed end and a second end; igniter means provided in said comhustion chamber in the region of said closed end; exhaust conduit means connected with said second end and constituting a resonator; and conduit means for admitting into said combustion chamber a mixture of fuel and oxygen, said cond'uit means comprising a substantially ladle-shaped outlet portion located in said comhustion chamber intermediate said ends thereof and having an open side facing said closed end.

2. A combination as defined in claim 1, wherein said outlet portion is nearer to said closed end than to said second end of said comhustion chamber.

3. A combination as defined in claim 1, wherein the area of the open side of said outlet portion at most equals half the cross-sectional area of that portion of said combustion chamber Which `accommoclates said outlet portion.

4. A combination as defined in claim 1, Wherein said conduit means comprises a tubular portion adjacent to said open side and located in said comhustion chamber, said tubular portion having a flat facing the closed end of said comhustion chamber.

5. A combination as defined in claim 4, wherein said fiat tapers in a direction away from said open side.

6. A combination as defined in claim 1, wherein said comhustion chamber comprises a wall at said closed end thereof, said wall having a concave ntemal surface facing the open side of said outlet portion.

7. A combination as defined in claim 1, Wherein said comhustion chamber is of vsubstantially circular crosssectional Outline.

8. A combination as defined in claim 1, wherein said conduit means comprises a second portion extendng from said comhustion chamber and said outlet portion comprises a substantially beak-shaped extenson remote from the second portion of said conduit means and extending toward the closed end of said comhustion chamber.

9. A combination as defined in claim 1, wherein said comhustion chamber is a cylinder and said igniter means comprises a spark plug installed centrally in the closed end of said comhustion chamber, said conduit means comprising a second portion adjacent to said outlet portion and extending substantially radially through said cylinder.

10. A combination as defined in clairn 1, wherein said conduit means comprises 'an inlet portion located externally of said comhustion chamber and coupling means separably connecting said inlet portion with said combustion chamber.

References Cited UNITED STATES PATENTS 2,795,105 6/1957 Porter -39.77

FREDERICK L. MATTESON, JR., Primary Examner. E. G. FAVORS, Assistant Examner.

U.S. Cl. X.R. 60-39.77 

